Apple seeds first developer beta of OS X 10.10.4

There is very little specific information about what is in OS X 10.10.4, but it seems likely that it focuses on fixes and improvements. Apple notes that this build, 14E7f, improves stability, compatibility, and security.

Apple's last major release of OS X Yosemite, 10.10.3, added the Photos app to OS X, along with 300 new emoji characters and a host of fixes and improvements.

Source: Apple